Light emitting diode and a manufacturing method thereof, a light emitting device

ABSTRACT

An LED includes a first electrode, for connecting the LED to a negative electrode of a power supply and a substrate located on the first electrode in which a plurality of contact holes are formed extending through the substrate. The diameter of upper parts of the contact holes is less than the diameter of lower parts of the contact holes, and the contact holes are filled with electrode plugs connecting the first electrode to the LED die. The light emitting device includes the LED, and further includes a susceptor and an LED mounted on the susceptor. The manufacturing method includes forming successively an LED die and a second electrode on a substrate, patterning a back surface of the substrate to form inverted trapezoidal contact holes which expose the LED die, and filling the contact holes with conductive material until the back face of the substrate is covered by the conductive material.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application claiming priority toU.S. patent application Ser. No. 13/129,386 filed May 13, 2011, which isa national stage application of PCT/CN2010/080652, filed Dec. 31, 2010,which claims priority to Chinese Patent Application No. 201010538428.3,entitled “A light emitting diode and a manufacturing method thereof, alight emitting device”, and filed Nov. 9, 2010, the complete disclosuresof which are expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to semiconductor technology, andparticularly relates to a light emitting diode and a manufacturingmethod thereof, and a light emitting device.

BACKGROUND OF THE INVENTION

A light emitting diode (LED) is a semiconductor device which isactivated by current to generate light of various colors. The III-Vcompound semiconductors, such as gallium nitride (GaN), which have wideband gap, high luminous efficiency, high electron saturation driftvelocity, and stable chemical properties, have great applicationpotential in high-brightness blue light emitting diodes, blue laser andother optoelectronic devices areas, and have aroused wide attention.

However, semiconductor light emitting diodes have low luminousefficiency in the prior art. As for light emitting diodes withoutpackage, the luminous efficiency is only a few percent. A lot of energyinside the device can not be sent out, thereby not only causing energywaste, but also affecting lifetime of the device. Therefore, it is ofkey importance to improve the luminous efficiency of semiconductor lightemitting diodes.

Because of the above application requirements, a plurality of methodsfor improving the luminous efficiency of semiconductor light emittingdiodes have been applied in device structure, for example, surfaceroughness, Metal reflector structure, and so on. Chinese patentpublication No. CN1858918A discloses a kind of light emitting diodes andthe under surface of the light emitting diodes forms an omnidirectionalreflector structure, whereby the luminous efficiency of the lightemitting diodes is improved. However, the method disclosed in this priorart needs to form a film comprising a plurality of high refractive indexlayers and low refractive index layers stacked on the substrate, ofwhich the manufacturing process is very complex.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a light emitting diodehaving high luminous efficiency.

To achieve the object, the present invention provides a light emittingdiode, comprising: a first electrode adapted for connecting the LED anda negative electrode of a power supply, a substrate set on the firstelectrode and an LED die set on the substrate. A plurality of contactholes are formed extending through the substrate and the diameter ofupper parts of the contact holes is less than the diameter of lowerparts of the contact holes. The contact holes are filled with electrodeplugs which are for connecting the first electrode and the LED die.

Accordingly, the present invention provides a light emitting devicewhich comprises a light emitting diode described above, wherein thelight emitting device further comprises a susceptor and the LED ismounted on the susceptor.

Accordingly, the present invention provides a method for manufacturingthe LED, comprising: forming successively an LED die and a secondelectrode on a substrate; patterning a back surface of the substrate toform inverted trapezoidal contact holes which expose the LED die; andfilling the contact holes with conductive material till the back face ofthe substrate is covered by the conductive material.

In comparison with conventional technologies, the present invention hasthe following advantages:

1. The contact holes are formed in the substrate and the first electrodeis connected to the LED die through the electrode plugs formed in thecontact holes, which reduces the current density, thus reducing theauger recombination and improving the internal quantum efficiency of theLED;

2. The diameter of upper parts of the contact holes is less than thediameter of lower parts of the contact holes and a sidewall of thesubstrate is adapted for reflecting the light emitting from the LED dieto a light exiting surface of the LED, which improves the luminousefficiency of the LED.

3. It is unnecessary for the method described above to form a multilayerfilm, therefore the manufacturing method is relatively easy toimplement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a light emitting device in the firstembodiment;

FIG. 2 is a flow chart of a method for manufacturing a light emittingdiode in the first embodiment;

FIG. 3 to FIG. 8 are sectional views of an embodiment of an LED formedby the method for manufacturing an LED in the present invention;

FIG. 9 is a flow chart of the step S2 in the first embodiment accordingto the method shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereunder, the present invention will be described in detail withreference to embodiments, in conjunction with the accompanying drawings.

Although the present invention has been disclosed hereinafter as abovewith reference to preferred embodiments in details, the presentinvention can be implemented in other embodiments which are different.Therefore, the present invention should not be limited to theembodiments disclosed here.

As taught in the background of the invention, in order to improve theluminous efficiency of semiconductor light emitting diodes, the methoddisclosed in the prior art needs to form a film comprising a pluralityof high refractive index layers and low refractive index layers stackedon the substrate, and the production process of the film is verycomplex.

In order to solve this problem, the present invention provides a lightemitting device comprising a light emitting diode. The light emittingdiode comprises: a first electrode adapted for connecting the LED and anegative electrode of a power supply, a substrate set on the firstelectrode and an LED die set on the substrate. A plurality of contactholes are formed passing through the substrate, and the diameter ofupper parts of the contact holes is less than the diameter of lowerparts of the contact holes. The contact holes are filled with electrodeplugs which are for connecting the first electrode and the LED die. Thefirst electrode is connected to the LED die through a plurality ofelectrode plugs formed in the contact holes, which reduces currentdensity and Auger recombination, thereby improving the internal quantumefficiency and increasing the luminous efficiency of the LED.

FIG. 1 is a schematic view of a light emitting device in the firstembodiment. The light emitting device comprises a susceptor 101 and anLED 109 set on the susceptor, wherein the susceptor comprises aninstallation pit for accommodating the LED 109. An angle θ formed by asidewall of the installation pit and a bottom wall of the installationpit ranges from 130° to 150°. The sidewall of the installation pit isadapted for reflecting the light emitting from the LED 109 to a lightexiting surface of the LED 109, which improves the luminous efficiencyof the light emitting device.

The susceptor 101 uses conductive material having good heat dispersioncharacteristics, which can disperse the heat from the LED andelectrically connect the LED 109 and the negative electrode of a powersupply.

Specifically, the susceptor 101 is made from materials such as siliconor aluminium, etc. The diameter of upper parts of the contact holes is 4μm, and the diameter of lower parts of the contact holes is 2 μm. Theinstallation pit has a large upper contact hole and a small bottomcontact hole, which guarantees that the angle θ formed by the innersidewall of the installation pit and the bottom wall of the installationpit is 130°˜150° and the sidewall of the installation pit reflects lightemitted form LED to light exiting surface of the light emitting device.

Preferably, the susceptor 101 also connects a first lead, which is usedto connect the susceptor 101 to the negative electrode of the powersupply.

The LED 109 is positioned in the installation pit of the susceptor 101.The LED 109 includes: a first electrode 102, a substrate 103 located onthe first electrode 102, an LED die located on the substrate 103, and asecond electrode 108 located on the LED die.

The first electrode 102 is positioned on the bottom of the installationpit of susceptor 101. The first electrode 102 is used to electricallyconnect the LED 109 and a negative electrode of the power supply.Specifically, the first electrode 102 is made from conductive metals,such as titanium, aluminum or gold, etc. Optionally, the first electrode102 covers the sidewall of the susceptor 101, which increases thecontact area of the first electrode 102 and the susceptor 101, therebyachieving good electrical connection.

A plurality of contact holes which extends through the substrate 103 areformed in the substrate 103. Electrode plugs 104 are formed in thecontact holes, which are used to connect the first electrode 102 to theLED die. Specifically, the substrate 103 is made up of sapphire, and theelectrode plugs 104 are made up of conductive metals, such as titanium,aluminum or gold, etc. The contact holes are evenly distributed in thesubstrate 103. The electrode plugs 104 are adapted for connecting thefirst electrode 102 to the LED die, which reduce the current density andauger recombination, thus improving the internal quantum efficiency andluminous efficiency of the LED.

The LED die is above the contact holes, and the first electrode 102 isbelow the contact holes. The cross section of the contact holes istrapezoidal, and the diameter of upper parts of the contact holes isless than the diameter of lower parts of the contact holes. According tothis embodiment, the diameter of lower parts of the contact holes rangesfrom 5 μm to 20 μm. The diameter of upper parts of the contact holes isless than the diameter of lower parts of the contact holes, whichguarantees that the sidewalls surrounding the contact holes form acertain degree with respect to the bottom surface of the contact holes,and the sidewalls reflect light emitted form LED die to light exitingsurface of LED, which improves the luminous efficiency of the LED.

An n-type semiconductor layer 105, an active layer 106 and a p-typesemiconductor layer 107 which are successively located on the substrate103 and the buffer layer 104 constitute the LED die. The material of then-type semiconductor layer 105 includes n-type gallium nitride, and theactive layer 106 includes multi-quantum well active layer. Specifically,the material of the multi-quantum well active layer includes InGaN, andthe material of the p-type semiconductor layer 107 includes p-typegallium nitride.

The second electrode 108 is located on the LED die, which is used toelectrically connect the LED 109 and a positive electrode of the powersupply. Specifically, the second electrode 108 is made from conductivemetals, such as nickel or gold, etc. Preferably, the second electrode108 is connected with a second lead; the second lead is used to connectthe LED 109 to the positive electrode of the power supply.

Preferably, the light emitting device further includes a lens structure110, which covers the LED and is adapted for converging light emittedfrom the LED 109, thereby improving the lightness of the light emittingdevice. Preferably, the lens structure 110 fills the gap between the LED109 and the susceptor 101. Specifically, the lens structure 110converges the light emitted from the LED (shown as light path B), thelight emitted from the LED die and reflected by the sidewall of thesusceptor, or reflected by the first electrode (shown as light path A),and the light emitted from the LED die and reflected by the sidewalls ofthe inverted trapezoidal components of the substrate (shown as lightpath C), thus improving the lightness of the light emitting device.

The light emitting device further includes fluorescent powder (nowshown) covering the lens structure, which is used for emitting whitelight. Specifically, for blue-light LED, the fluorescent powder is YAGfluorescent powder including Ce3+.

There is also provided a method for manufacturing an LED in the presentinvention. FIG. 2 is a flow diagram of an embodiment of the method formanufacturing an LED. The method includes:

-   -   S1, forming on a substrate an LED die and a second electrode        successively;    -   S2, patterning a back surface of the substrate to form inverted        trapezoidal contact holes which expose the LED die;    -   S3, filling the contact holes with conductive material till the        back face of the substrate is covered by the conductive        material.

FIG. 3 to FIG. 8 are sectional views of an embodiment of an LED formedby the method for manufacturing an LED in the present invention; eachstep is described below in more detail in conjunction with theaccompanying drawings.

Referring to FIG. 3, in step S1, the substrate is sapphire.Specifically, by using a Metal-organic Chemical Vapor Deposition (MOCVD)process, an n-type semiconductor layer 207, an active layer 208 and ap-type semiconductor layer 209 are deposited on a substrate 201. Then-type semiconductor layer 207, the active layer 208 and the p-typesemiconductor layer 209 constitute the LED die. The material of then-type semiconductor layer 207 includes n-type gallium nitride, and theactive layer 208 includes multi-quantum well active layer. Specifically,the material of the multi-quantum well active layer includes InGaN, andthe material of the p-type semiconductor layer 107 includes p-typegallium nitride.

Referring to FIG. 4, still in step S1, a second electrode is formed inthe LED die. The second electrode includes nickel or gold, and is formedthrough a Physical Vapor Deposition process or an E-gun evaporationprocess.

Preferably, before performing the step S2, a thickness reduction processis performed on the back face of the substrate 201. Specifically, thethickness reduction process is chemical mechanical polishing (CMP). Thethickness of the substrate 201 is reduced to 20˜50 nm. The thicknessreduction process which reduces the thickness of the substrate 201benefits the later patterning process, and makes the substrate 201 easyfor patterning.

Referring to FIG. 9, which is a flow diagram of a preferable embodimentof the step S2 in FIG. 2, the step S2 includes:

-   -   S21, forming a hard mask on the back face of the substrate;    -   S22, etching the back face of the substrate using the hard mask        as an etching mask, to form a plurality of inverted trapezoidal        contact holes until the LED die is exposed;    -   S23, removing the hard mask.

Referring FIG. 6, step S21 includes: depositing hard mask material onthe back face of the substrate 201, and then patterning the hard maskmaterial by photo-etching and etching to form a hard mask 206.Specifically, the hard mask 206 is made from silicon dioxide.

Referring to FIG. 7, step S22 includes: wet etching the substrate 201from the back face of the substrate 201 using the hard mask 206 as anetching mask to form a plurality of inverted trapezoidal contact holeson the regions not covered by the hard mask 202, until the LED die isexposed by all the contact holes. Specifically, the substrate issapphire, and an anisotropic etching is performed to the sapphiresubstrate with a mixed solution of sulfuric acid and phosphoric acid.

It should be noted that the solution used in wet etching has a highselection ratio to the substrate 201, to avoid etching the hard mask206. Specifically, the substrate 201 is a sapphire substrate (aluminumoxide), the hard mask 206 is silicon dioxide, and the substrate 201 isetched with a mixed solution of sulfuric acid and phosphoric acid, whichhas a small corrosive action upon silicon dioxide.

In step S23, the hard mask 206 includes silicon dioxide and is removedwith hydrofluoric acid solution.

As for the step S1, preferably, adjacent hard mask patterns in the hardmask 206 have an interval of 0.1˜10 μm, and the depth of the contacthole is the same as the substrate 201. Specifically, the depth of thecontact holes ranges form 20 μm to 50 μm; the diameter of lower parts ofthe contact holes ranges form 5 μm to 20 μm.

Referring to FIG. 8, in step S3, the contact holes are filled and filledup with conductive material by Physical Vapor Deposition (PVD); and aconductive material layer is formed overlying the back face of thesubstrate, which forms a first electrode 202. The conductive materialfilled in the contact holes forms electrode plugs of the first electrode202. The first electrode 202 electrically connects to the n-typesemiconductor layer 207 through the electrode plugs. Specifically, theconductive material is conductive metal, such as titanium, aluminum orgold, etc.

The method for manufacturing an LED is finished.

The method for manufacturing a light emitting device which includes anLED further includes steps: providing a susceptor, the susceptorincluding an installation pit; and fixing an LED on the bottom of theinstallation pit of the susceptor, in a way that the first electrode isconnected with the bottom of the installation pit. The inner side walland a bottom of the installation pit forms an angle of 130°˜150°, whichinner side wall reflects light from the LED, thus improving the luminousefficiency of the LED. The susceptor is made from conductive materialhaving good heat dispersion characteristics, such as silicon oraluminium. The dimension of the upper opening of the installation pit is4 μm, and the dimension of the bottom opening of the installation pit is2 μm.

The method for manufacturing a light emitting device further includes:forming a lens structure covering the second electrode. Preferably, thelens structure is formed covering the second electrode and filling thegap between the LED and the susceptor. The lens structure converges thelight emitted from the LED.

The method for manufacturing a light emitting device further includes:coating the lens structure with fluorescent powder, which is used toemit white light. For blue-light LED, the fluorescent powder is YAGfluorescent powder including Ce3+, which is used to emit white light.

Preferably, the method for manufacturing a light emitting device furtherincludes: coating the sidewalls with conductive material, and theconductive material is connected to the first electrode (as shown inFIG. 1), which increases the contact areas of the first electrode andthe susceptor, thereby achieving good electrically connection.

The method for manufacturing a light emitting device further includes:providing a first lead which connects the susceptor to the negativeelectrode of a power supply, and providing a second lead which connectsthe second electrode to the positive electrode of a power supply.

A light emitting device has been manufactured.

The method provided in the present invention is easy to implement.

Although the present invention has been disclosed as above withreference to preferred embodiments thereof but will not be limitedthereto. Those skilled in the art can modify and vary the embodimentswithout departing from the spirit and scope of the present invention.Accordingly, the scope of the present invention shall be defined in theappended claims.

What is claimed is:
 1. A method for manufacturing an LED comprising:forming successively an LED die and a second electrode on a substrate,wherein the substrate is sapphire; patterning a back surface of thesubstrate to form inverted trapezoidal contact holes which expose theLED die; and filling the contact holes with conductive material untilthe back face of the substrate is covered by the conductive material;wherein patterning a back surface of the substrate to form invertedtrapezoidal contact holes which expose the LED die comprises: forming ahard mask on the back face of the substrate, wherein the hard mask issilicon dioxide; performing an anisotropic etching to the upper surfaceof the sapphire substrate with a mixed solution of sulfuric acid andphosphoric acid using the hard mask as an etching mask to form aplurality of inverted trapezoidal contact holes until the LED die isexposed; and removing the hard mask with a hydrofluoric acid solution.2. The method for manufacturing an LED of claim 1, wherein beforepatterning the back surface of the substrate, the method furthercomprises a thickness reduction process of the substrate from the backface of the substrate.
 3. The method for manufacturing an LED of claim1, wherein a step of filling the contact holes with conductive materialcomprises: filling the contact holes with conductive material byphysical vapor deposition.